Conventional Public Switched Telephone Network (PSTN) may provide card call services such as phone card 201 and 300 services. Along with the development of telecommunication technologies, it is a trend to merge communication networks including the PSTN with one another, which gives birth to Next Generation Network (NGN). As a service-driven network, NGN may provide a variety of services including intelligent services. A card call service supporting a card call is one of the intelligent services which may be provided by NGN.
The basic principle for implementing a card call service in NGN is shown in FIG. 1. A user employs a calling user terminal registered in NGN to initiate a call request, in order to access a call processing server. The call processing server reads calling information carried in the call request, authenticates the calling user terminal based on the calling information, reads the prefix of the called number carried in the call request if the calling user terminal is valid, determines that the calling user terminal has initiated a card call according to the obtained prefix of the called number, and then forwards the call request to an Intelligent Network (IN) server.
Upon receipt of the call request, the IN server applies for a dedicated media channel via an internal or external Media Resource Server (MRS), and adopts the dedicated media channel to instruct the user via the calling user terminal to input the serial number and password of a card. When the IN server receives the serial number and password of the card with the number receiving function of the MRS, the IN server authenticates the serial number and password of the card and checks whether the deposit corresponding to the serial number and password of the card in a database may support the card call. At least one of the serial number and password of the card and the deposit supporting the card call are named as card information which may support the card call.
Having determined that the serial number and password of the card are correct and the deposit is sufficient to implement a card call, the IN server forwards the call request to the called user terminal. After the called user terminal returns a call response to the IN server indicating that the call is accepted by a called user, the IN server sends a call Acknowledgment (ACK) message to the called user terminal and establishes a media channel which connects the IN server and the called user terminal to enable the calling user terminal and the called user terminal to carry out the subsequent communication.
If a call processing server determines that the calling user terminal is invalid, the call request sent from the calling user terminal is rejected. Specifically, the method of the authentication includes: determining whether the calling information provided by the calling user terminal matches user terminal information which is registered and saved in the database, determining that the calling user terminal is valid if the calling information provided by the calling user terminal matches the user terminal information; otherwise, determining that the calling user terminal is invalid.
It can be seen that NGN may implement the card call service on the premise that the calling user terminal should provide the calling information when initiating a call and pass the authentication, which actually inherits the communication feature of PSTN and brings out a variety of defects into the card call service provided by NGN.
The defects are brought out due to the following reasons. Unlike the twisted pair line access mode used by PSTN, NGN is a communication network based on Internet Protocol (IP). Thus, unlike PSTN which merely provides services for registered user terminals, NGN not only provides services for the registered user terminals but also for a larger number of unregistered user terminals which communicate based on IP. However, calling information provided by the unregistered user terminals when initiating card calls may not match user terminal information registered in the database.
It can be seen that NGN may not provide card call services for a large number of unregistered user terminals which initiate card calls whether the unregistered user terminals have card information which may support the card calls. Practically, if a large number of card call services are rejected, it certainly reduces the satisfaction of users, and holds operators back from promoting the card call services, severely impedes the development of services provided by the operators, and impairs the development of NGN services.